These are the soils formed from the material transported by the pull of gravity. Fragments from cliffs or steep rocky slopes become dislodged from time to time and may accumulate below. This material is characteristically very coarse, consisting mostly of large fragments of rock and has a rather steep and unstable surface. The other kind of movement of weathered rock materials is due to landslides. These usually result from heavy rain or earth tremors and as a result the materials start cascading down a steep slope. Colluvial soils are devoid of any stratification and represent a random assortment of soil particles and rock fragments. Particles of different sizes, including various kinds of rocks,and soils derived from slopes or cliffs are mixed indiscriminately.